The objective of this research is to test the hypothesis that the various "threat" behaviors which precede overt attack in hamsters represent different levels of aggressive motivation. To do so, intracranial stimulation (ICS) thresholds for elicited attack will be determined during each of these behaviors. It is predicted that ICS thresholds determined during a given behavior will be inversely related to the probability that the given behavior precedes overt attack in control (unstimulated) sessions. A preliminary, methodological experiment will be performed first to determine if a hamster model may be substituted for a live target animal in the major experiment.